1. Field of the Invention
The present invention relates to an MOS-controlled semiconductor component having a structure that assures a good switching behavior of the component without deteriorating its static properties.
2. Description of the Prior Art
As voltage-controlled components, power MOSFETs do not require a control current in the stationary operating condition. Due to their structure, however, power MOSFETs contain comparatively large parasitic capacitances that must be charge-reversed at every switching event. Since these capacitances, which influence the switching behavior of the MOSFET, are composed of both metallizations and insulator layers, as well as of the space-charge zones forming in the region of the pn-junctions, their respective size depends on the applied voltage in a non-linear way.
In known MOS-controlled power semiconductors (MOSFETs, IGBTs), the reactance capacitance produced by tile gate electrode and the insulator of the gate-drain or of the gate-collector overlap area has a substantially disadvantageous effect on the switching behavior of the respective component and its switching environment (freewheeling branch). In particular, thus, the switching speed, the control performance, the rise rate, the dynamic strength and the dissipated power of the component are negatively influenced by the parasitic properties of the reactance capacitance.
The gate-drain or gate-collector overlap area and, thus, the reactance capacitance in MOS-controlled components can be made clearly smaller by a modification of the gate structure (see B. Jayant Baliga: Modern Power Devices, John Wiley & Sons (1987), pages 300 through 305). Although this measure improves the high-frequency behavior of the respective component, it also significantly deteriorates its breakdown strength (see Modern Power Devices, pages 274-276, particularly FIG. 6.10). Attempts to reduce the reactance capacitance with a thicker gate oxide without significantly lowering the blocking voltage were also unsuccessful.